Need support Vector4 for uv attribute

[eliiik]

public List<Vector2> _UVs = new List<Vector2>(); public List<Vector2> _UV2s = new List<Vector2>(); public List<Vector2> _UV3s = new List<Vector2>();
(Code from HEU_MeshData.cs)

Currently, the uv attribute will convert to Vector2 type in Houdini Engine Unity. But in some cases, especially VFX stuffs, it is quite useful to store some more information in uv.2, uv.3.
I change some code in the source file of Houdini Engine Unity code and it works well. I think uv attribute shouldn't be limited in Vector2 only.

And now Unity support mostly 8 uv channels in one mesh, I think it should be concerned, too.